An Evaluation of Supramaximally Loaded Eccentric Leg Press Exercise

TL;DR: The information gathered in the study provides a foundation for practitioners to consider when devising loading strategies and implementing or evaluating supramaximally loaded eccentric exercise when using a similar exercise and device.

Abstract: Harden, M, Wolf, A, Russell, M, Hicks, KM, French, D, and Howatson, G. An evaluation of supramaximally loaded eccentric leg press exercise. J Strength Cond Res 32(10): 2708-2714, 2018-High-intensity eccentric exercise is a potent stimulus for neuromuscular adaptation. A greater understanding of the mechanical stimuli afforded by this exercise will aid the prescription of future eccentric training regimens. This study sought to investigate the mechanical characteristics of supramaximally loaded eccentric exercise when using a custom-built leg press machine. Using a within-subject, repeated-measures design, 15 strength trained subjects (age, 31 ± 7 years; height, 180.0 ± 6.8 cm; body mass, 81.5 ± 13.9 kg) were assessed under 3 different conditions: low (LO), moderate (MOD), and high (HI) intensity, which were equivalent in intensity to 110, 130, and 150%, respectively, of peak force during an isometric maximal voluntary contraction (IMVC) performed on leg press at 90° knee flexion. All loading conditions demonstrated a similar pattern of mechanical profile; however, the variables underpinning each profile showed significant (p < 0.01) load-dependent response (LO vs. MOD, MOD vs. HI, LO vs. HI) for all variables, except for average acceleration. Average force associated with each loading conditions exceeded IMVC but equated to a lower intensity than what was prescribed. Repetitions under higher relative load intensity stimulated greater average force output, faster descent velocity, greater magnitude of acceleration, shorter time under tension, and a decline in force output at the end range of motion. This research provides new data regarding the fundamental mechanical characteristics underpinning supramaximally loaded eccentric leg press exercise. The information gathered in the study provides a foundation for practitioners to consider when devising loading strategies and implementing or evaluating supramaximally loaded eccentric exercise when using a similar exercise and device.

Summary

INTRODUCTION

• Eccentric resistance exercise classically involves resisting an external load during the descending phase of an exercise movement.
• Modification and instrumentation of the inclined leg press device removed the potential limitations associated with high intensity eccentric training practice, such that it was possible to apply very high loads eccentrically and allow an investigation of the fundamental mechanics associated with this mode of exercise.
• The range of intensities were chosen to ensure that manipulation in external load (independent variable, IV) was sufficiently different enough to produce mechanical differences in the kinetic and kinematic parameters (dependent variable, DV).
• A smaller intensity range may have produced similar data across conditions thus making it difficult to draw meaningful conclusions for coaching and research practice.

Subjects

• All subjects were from a strength-power sport background e.g., Olympic weightlifting, rugby, athletics and track sprint cycling, with 11 ± 7 years of resistance training experience, which had included phases of maximum strength training.
• All subjects were free from musculoskeletal injury for at least 12 months before the study started, and reported no musculoskeletal or cardiovascular disorders.
• The volunteers were required to avoid unaccustomed exercise during the whole study period, refrain from strenuous exercise in the 48 hours prior to attending each testing and were instructed to attend each session in a well-hydrated and fed state, having abstained from alcohol in the preceding 24 hours.
• Subjects were informed of the benefits and risks associated with the investigation, as well as all study procedures prior to providing written, informed consent.
• The study procedures and consent documentation was approved by University Ethics Committee in accordance with The Declaration of Helsinki.

Procedures

• The custom-built 45° incline leg press machine (Sportesse, Somerset, UK) facilitates performance and assessment of concentric, isometric and eccentric exercise .
• The isometric function of the leg press operates via an inbuilt locking mechanism that can secure the carriage at any position along the machines framework.
• The load cells and potentiometers sampled at 200 Hz.
• Securing the leg press carriage at 90° of the subjects’ knee flexion (verified by goniometry), they completed 3 x 1 repetition at each of the following perceived intensities; 50%, 75% and 100% for 3 seconds per repetition.
• Preceding the LO trial an additional 1 repetition with an external load equivalent to 100% IMVC was completed, preceding the MOD trial an additional 1 repetition with an external load equivalent to 110% IMVC was completed, and preceding the HI trial an additional 1 repetition with an external load equivalent to 130% IMVC was completed.

Statistical Analyses

• Intraclass correlation coefficients (ICC) and coefficients of variation (CV, %) including 95% confidence intervals were calculated to determine the repeatability of eccentric performances between 2 repetitions (7).
• Using SPSS (Version 24.0; SPSS Inc, Chicago, USA) a repeated measures ANOVA was used to determine significant differences in the DV’s; force (average and end), TUT, velocity and acceleration between each loading condition (IV) and where appropriate, a Bonferroni post-hoc test.
• Group data are presented as mean ± SD with 95% confidence intervals (CI).

RESULTS

• Average force associated with each loading conditions exceeded IMVC peak force but was less than the prescribed external force.
• All loading conditions demonstrated a similar pattern of mechanical profile , however, the variables underpinning each profile showed significant (p < 0.01) load dependent response (LO vs MOD, MOD vs HI, LO vs HI) for all variables, except for average acceleration which was significantly different between LO and HI, only (p = 0.05) (Table 1).
• Force at the end ROM was 1%, 3% and 5% less than the average force measured over the ROM for LO, MOD and HI trials respectively.

DISCUSSION

• The aim of this research was to investigate the fundamental mechanical characteristics associated with supramaximal intensity eccentric leg press exercise.
• The results showed that the heavier relative external load stimulated greater average force output which, in turn, was associated with a faster descent velocity and shorter TUT.
• Because of this, the intensity of the supramaximal load was less than the prescribed 110, 130 and 150% relative to peak force exerted during the IMVC.
• To understand the acute and chronic responses to this type of eccentric exercise and the different force-TUT interactions more research is warranted, particularly given the growing interest in elite sport to maximize adaptation from eccentric loading.
• This would enable practitioners to accurately determine an individual’s eccentric force producing capacity and prescribe eccentric training more accurately.

PRACTICAL APPLICATIONS

• Overall, supramaximally loaded eccentric-only exercise appears to offer a unique and potent stimulus; individuals can be exposed to extended TUT at high levels of force that exceed what more traditional regimes might offer.
• When implementing supramaximal loaded eccentric-only repetitions, practitioners should be mindful to prescribe a load that is well tolerated in the restricted portion (end ROM) of the exercise movement to facilitate continued force production and maintenance of muscular tension for sustained and consistent movement.
• This study has addressed the acute mechanical response to supramaximally loaded eccentric-only exercise under different magnitudes of external load.
• As the experimental approach was devised with practical application in mind, the results provide strength coaches and applied practitioners with a greater understanding of the mechanical demand imposed by supramaximally loaded eccentric-only leg press exercise.
• Importantly, these data provide new insight into the performance response from strength-trained individuals throughout supramaximal eccentric leg press exercise.

Author contributions

• MH, DF, MR, GH, also known as Experiment planning and design.
• Data collection: MH. Data Analysis: MH, GH.
• MH, GH, AW, KH, also known as Interpreted results of research.

Figure Legends

• Table 1. Mechanical characteristics of eccentric leg press repetitions during LO, MOD and HI intensity loading conditions Figure 1.
• Incline leg press with; (A) unilateral force plates, (B) air compression unit, (C) removable steel bar insert, (D) safety pins, (E) adjustable seat.
• Underneath the foot carriage; (F) adjustable ROM sensors, also known as Right photo.
• A representative mechanical profile for a single eccentric leg press repetition under three supramaximal loading conditions.
• Black solid line: LO intensity loading condition, dark grey solid line: MOD intensity loading condition, light grey solid line:.

Figures

Figure 2.

Figure 1.

TABLE 1. Mechanical characteristics of eccentric leg press repetitions during LO, MOD and HI intensity loading conditions

Full text

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1
JSCR-08-10057 R1
AN EVALUATION OF SUPRAMAXIMALLY LOADED ECCENTRIC LEG PRESS
EXERCISE

2

3
AN EVALUATION OF SUPRAMAXIMALLY LOADED ECCENTRIC LEG PRESS
EXERCISE
Running title: Mechanical characteristics of eccentric exercise
Mellissa Harden
1,2
, Alex Wolf
2
, Mark Russell
5
, Kirsty M Hicks
1
, Duncan French
4
, Glyn
Howatson
1,3
1
Department of Sport Exercise and Rehabilitation, Faculty of Health and Life Sciences,
Northumbria University, UK
2
English Institute of Sport, UK
3
Water Research Group, School of Environmental Sciences and Development, Northwest
University, Potchefstroom, South Africa
4
UFC Performance Institute, USA
5
School of Social and Health Sciences, Leeds Trinity University, Leeds, UK
Corresponding author:
Glyn Howatson, PhD
Department of Sport, Exercise and Rehabilitation
Faculty of Health and Life Sciences
Northumbria University
Newcastle upon Tyne, UK
Tel: +44 (0) 191 227 3575
Email: glyn.howatson@northumbria.ac.uk
Funding: This work was completed under a joint funded doctoral studentship between the
English Institute of Sport and Northumbria University.
Laboratory: HSBC National Cycling Centre, English Institute of Sport, Manchester, UK

4
ABSTRACT
High intensity eccentric exercise is a potent stimulus for neuromuscular adaptation. A greater
understanding of the mechanical stimuli afforded by this exercise will aid the prescription of future
eccentric training regimes. This study sought to investigate the mechanical characteristics of
supramaximally loaded eccentric exercise when using a custom-built leg press machine. Using a
within subject, repeated measures design, 15 strength trained subjects (age 31 ± 7 years; height
180.0 ± 6.8 cm; body mass 81.5 ± 13.9 kg) were assessed under three different conditions; LO,
MOD and HI which were equivalent in intensity to 110, 130 and 150%, respectively, of peak force
during an isometric leg-press at 90° knee flexion (IMVC). All loading conditions demonstrated a
similar pattern of mechanical profile, however, the variables underpinning each profile showed
significant (p < 0.01) load dependent response (LO vs MOD, MOD vs HI, LO vs HI) for all
variables, except for average acceleration. Average force associated with each loading conditions
exceeded IMVC, but equated to a lower intensity than what was prescribed. Repetitions under
higher relative load intensity stimulated greater average force output, faster descent velocity,
greater magnitude of acceleration, shorter TUT and a decline in force output at the end range of
motion. This research provides new data regarding the fundamental mechanical characteristics
underpinning supramaximally loaded eccentric leg press exercise. The information gathered in
the study provides a foundation for practitioners to consider when devising loading strategies, and
implementing or evaluating supramaximally loaded eccentric exercise when using a similar
exercise and device.
Keywords: maximal force, load prescription, muscle lengthening

Frequently asked questions

Q1. What are the contributions in this paper?

This study sought to investigate the mechanical characteristics of supramaximally loaded eccentric exercise when using a custom-built leg press machine. This research provides new data regarding the fundamental mechanical characteristics underpinning supramaximally loaded eccentric leg press exercise. The information gathered in the study provides a foundation for practitioners to consider when devising loading strategies, and implementing or evaluating supramaximally loaded eccentric exercise when using a similar exercise and device. 

Q2. What are the future works in this paper?

As such, it seems apt to suggest that future research should establish task-specific methods of eccentric assessment.